The most common technique for coronary artery bypass graft (CABG) surgery requires arresting the heart and attaching a patent to a cardiopulmonary bypass machine to preserve the flow of oxygenated blood during the procedure. This technique also requires splitting the sternum, followed by placing large bore cannulas in the arterial and venous sides of the heart to circulate blood through an extracorporeal pump. The heart is chilled to reduce the myocardial oxygen demand and the bypass graft is installed on a non-beating heart. The common technique is lengthy and traumatic to the patient and carries all of the attendant risks of cardiopulmonary bypass.
In recent years, surgeons have begun performing CABG surgery on the beating heart, without the use of extracorporeal circulation. The beating heart CABG procedure uses smaller incisions, avoids the use of the extracorporeal pumps, and permits the graft procedure to be accomplished without splitting the sternum. When the beating heart CABG procedure is employed, a number of advantages are observed: patients who are treated without extracorporeal circulation recuperate faster, the hospital stay is shorter and less costly, the need for a postoperative mechanical ventilator is reduced, and the amount and frequency of blood transfusions is also reduced.
Despite the advantages, the beating-heart CABG procedure is not widely practiced, in part, because of the difficulty in performing the necessary surgical procedures while the heart is still beating using conventional instruments. If special designed instruments were available to assist the surgeon in performing the CABG procedure on the beating heart, the procedure would be more widely practiced and the treatment of a significant patient population would be improved.
These instruments must be specially designed to facilitate less invasive procedures where minimally sized incisions are placed in the chest. In many surgical procedures, such as the beating-heart CABG procedure, the instrument must be manipulated through a comparatively small opening in the chest and at a distance of at least several inches from the tissue being incised. Thus, instruments must be specially designed to enable the surgeon to complete all the phases of the surgery by remote manipulation through small openings in the chest cavity. Additionally, because the heart may remain beating throughout the operation, the procedures must be performed quickly, and without undue trauma to the tissue, and must not cause excess loss of blood.
In many surgical procedures, including the beating-heart CABG procedure, the surgeon must make a substantially linear incision in a vessel, such as an artery which carries blood to the heart. The incision must completely penetrate a portion of one side of the wall of the vessel to create an opening without damaging the surrounding tissue, including in particular, the interior walls of the vessel proximate to the site of the incision. In the CABG procedure, it is particularly important for the surgeon to create a straight, uniform incision through a portion of the vessel wall because a precise incision through the wall of a vessel is necessary to create the opening to which an anastomosis will be sewn and through which blood ultimately will flow. In such cases, the surgeon creates an incision in a vessel to receive the anastomosis, which is completed when the connection is sewn to the periphery of the opening in the artery to re-establish blood flow.
Currently, many surgeons begin making the incision in the artery with a scalpel or with the point of a pair of surgical scissors and then manually cut the incision to the desired length by a series of scissor cuts or by manually passing the scalpel through the wall of the vessel for the entire length of the incision. These current techniques have several disadvantages which are particularly problematic in a beating-heart procedure. In cardiac surgery on the beating heart, the surgical field is small, and it is difficult for the surgeon to precisely manipulate the instruments. The surgeon must make a clean incision completely through one wall of a small vessel without damaging the interior surface of the vessel opposite the location of the incision or the surrounding tissue. The current techniques are also time consuming, imprecise in creating an incision of an exact length, and may cause undue trauma to the surrounding tissue, especially when the tissue is moving due to the motion of the heart. Because blood flow through the vessel may be interrupted during the beating heart CABG procedure, it is also important that the entire incision be made rapidly. If the current techniques result in an incision which is poorly formed, this may lengthen the procedure and adversely affecting the patency of the graft when it is sewn to the periphery of the incision.
This invention is surgical instruments which facilitate precise and substantially linear incisions, especially through the wall of vessels, such as arteries, and which have been specially designed for coronary artery bypass graft procedures (CABG) on the beating heart. The instruments of this invention are particularly useful to create the incision in the target artery to complete an anastomosis, typically the left anterior descending artery (LAD), although the actual site for any particular patient is determined clinically. The instruments of the invention allow incisions to be rapidly made, precisely measured, and cleanly formed so that the bypass graft can be rapidly sewn in place. The instruments of the invention also result in less trauma to the vessel and require fewer manipulations of the vessel by the surgeon. This can be particularly significant where the interior of the vessel contains lesions or deposits. Although features of the instruments of the invention have particular utility for beating-heart CABG procedures, the instruments described here can be advantageously used in other procedures where similar conditions to the beating-heart CABG procedure exist.
In one embodiment, the invention is a hand-held instrument with a curved cutting edge formed on the interior edge of a curved or arcuitous segment located near the end of the instrument. The tip of the instrument has a point for penetrating the vessel wall. The point may have several alternate shapes to facilitate penetration of the vessel wall while minimizing the trauma to the surrounding tissue. Alternatively, the cutting surface maybe disposed on one or more straight surfaces at the terminal end of the instrument.
Another embodiment is comprised of a hand-held instrument with a movable shaft member such that the incision is created by engaging a cutting edge against a blade stop with the tissue being cut therebetween. This instrument is also constructed to facilitate rapid linear incisions in a vessel while minimizing the possibility for damage to the surrounding tissue.
In another embodiment, the instrument features a motion-cancelling member which compensates for the movement of the target surface to be incised. This embodiment has a cutting blade which is manipulated from a handle which is isolated from the movement of the tissue containing :or proximate to the target of the incision.